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        <title>Document</title>
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        <div id="box"></div>
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    <script>
        // function fun() {
        //     this.age = 123
        //     // return this
        // }
        // console.log(fun())
        // let obj = new fun()
        // console.log(obj.age)
        // var obj = {
        //     age: 18,
        // }
        // console.log(window.Object.prototype)
        // console.log(obj.toString.call(obj))
        // function toString() {
        //     console.log(this.age)
        // }
        let arr = [1, 2, 3]
        // arr.push.call(arr, 8) //[(1, 2, 3, 8)]
        // function push(n) {
        //     this[3] = n
        // }
        // var date = new Date()
        console.log(arr)
        // let n = new Array()
        // console.log(window.Array.prototype.push)
        // let arr1 = [],
        //     arr2 = []
        // console.log(arr1)
        // var fakeArr = { 0: 'a', 1: 'b', length: 2 }
        // fakeArr.__proto__ = Array.prototype
        // console.log(fakeArr)
        // arr1.toString, arr2.toString
    </script>
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